Justification:
This species has a small distribution. It is harvested for commercial purposes and has experienced significant declines in portions of its range in the past. It is currently managed under fishing permits in California and there are management proposals for Baja California, Mexico. It has been estimated to have had a population reduction of approximately 50% in Baja California, and a minimum of 30% decline in California, based on exploitation levels in the Channel Islands. It is therefore estimated that a 30-40% decline has occurred across the species' entire range over the past 3 generation lengths and it is therefore listed as Vulnerable.

This species can be found from Baja California, Mexico to Monterey Bay, California. There are scattered occurrences up to Point Conception in California (Hamel and Mercier 2008). It occurs at depths between 0-60m (Conand 2006).

In the Channel Islands of California, densities before the start of the fishery were between 0.2 to 21.1 ind.10 m2 (Schroeter et al. 2001). After the fishery was open, densities were down by 33-83% in the same study area (Schroeter et al. 2001). Between 1983 and 1990, annual landings fluctuated between about 20,000 and 60,000 kg in California. In 1991, over 261,871 kg were harvested. Combined trawl and dive harvest peaked in 1996 at 380,703 kg with an ex-vessel value of USD 582,370 (Rogers-Bennett and Ono 2001). The increase in landings is associated with an increase in an effort, as this is an emerging fishery. There is also a displacement from traditional fisheries that has been banned, including abalone (Rogers-Bennett and Ono 2001).

In Baja California, P. parvimensis has been exploited since the early 1990s, and despite the fact that this species was exploited as much as I. fuscus, its populations have just begun to decline (Bruckner 2006).Densities in Baja California (Mexico), between Puerto Escondido and Punta Abreojos ranged from 0.01 ind/m2 to 0.26 ind/m2 (Fajardo-Leon and Turrubiates-Morales 2009). In another study area of Baja California between Santo Tomas and Santa Rosalita, densities were between 0.175 - 0.821 ind/ m2 (Salgado-Rogel et al. 2009).

P. parvimensis occurs in subtidal habitats on both rocky and soft habitats (Conand 2006). The spawning peak was recorded from February to May in Baja California. The species is found in low energy environments and it is most abundant in area with high organic content. Small individuals in Santa Catalina (California) were seen feeding on fine material collected from rock rubble under kelp. Juveniles (between 2 and 6 cm TL) are found under rocks only, whereas those individuals between 8 and 12 cm can be found both on and under rocks (Hamel and Mercier 2008).

Parastichopus parvimensis does not become sexually mature until it reaches ca. 40 g in total body weight (Muscat 1983). Weight at first maturity was 140 g at Isla Natividad and 120 g at Bahia Tortuga (Fajardo-Leon et al. 2008).This species expresses a definite reproductive cycle with spawning in May and June possibly in response to increasing water temperatures. The gonad is completely reabsorbed during September and October and the gonadal growing phase starts around January. The vitellogenic oocyte reach an average of 180 μm in diameter (Muscat 1983).

Yingst (1982) observed an annual evisceration cycle, which affected 60 % of individuals during October and November, causing them to cease feeding for about four weeks until minimum gut regeneration was accomplished. Muscat (1982) brought evidence of an annual pattern of intestinal growth and development, with sea cucumbers undergoing spontaneous evisceration in September and October. They can regenerate lost parts in one or two months, reaching a maximum overall body weight during the winter, probably due to resumed feeding and accumulation of gonad materials. There are dramatic seasonal fluctuations in population densities, with nearly complete disappearance from shallow water from August to November in Southern California (Muscat 1982). There appears to be a migration downslope from the warmer, shallower areas, which occurs on both hard rock and sand substrates. Eckert et al. (2001) indicates that P. parvimensis begin to settle after 28 days on under sides of rocks and kelp holdfast. Juveniles reached ca. 3.5 cm long after a year of growth.

Larger individuals avoid rocks; they dwell and feed on granular sediments. Densities of sea cucumbers increase on hard substrates, being up to ten times higher than on soft bottoms (Yingst 1982). Nonetheless, the largest specimens are found on sand (Muscat 1982).

Generation length is largely unknown for these species. Body size is not a good indicator of age or longevity. There is some indication, however, that many echinoderms do not go through senescence, but simply regenerate. Therefore generation length cannot be estimated, but is assumed to be greater than several decades (20-40 years) in a natural, undisturbed environment.

In the state of California, the fishery started in 1978 and focuses on two species: Parastichopus californicus and P. parvimensis. Both diving and targeted trawling are used for the capture, however trawls are restricted mainly to the south of the state and their use has declined over the past few years (Bruckner 2006). In 1997, divers with permits for sea urchins and abalones were allowed to collect sea cucumbers as well (Rogers-Bennett and Ono 2001, Bruckner 2006).

On the west coast of Baja California, the capture of P. parvimensis started in 1989 with 53 tons, and increased rapidly until 1992, when it peaked at 723 tons. In 1996 there was another peak of 637 tons, dropping to 350 tons in the following year. From 1998-2006, the capture was stable between 200-300 tons. During the reported period in this study, there has been a decline of approximately 50% (Salgado-Rogel et al. 2009). Because of high demand and ensuing overexploitation of the species, in 2002-4 it was put under a exploratory fishery scheme (Fajardo-Leon et al. 2008).

U.S. fisheries for this species are closely monitored and permits are required (Bruckner 2005). However, there are no quotas (Rogers-Bennett and Ono, 2001, Schroeter et al. 2001). There were 111 dive permits and 36 trawl permits in 1997 and it declined to 95 divers and 24 trawl permits in 2004 (Bruckner, 2005). Trawling is prohibited in conservation areas around most islands.

In California, since 1992-1993, a special permit has been required for harvesting sea cucumbers, at a cost of USD 250 per year. Permit recipients must have landed a minimum of 20 kg during the previous four-year period. In 1997, separate permits were issued for each gear type, with a limit on the total number of permits issued. A maximum of 111 dive permits and 36 trawl permits were issued in 1997, and this declined to 95 dive permits and 24 trawl permits in 2004. There are no restrictions on catch, but trawling is prohibited in the Trawl Rockfish Conservation Areas (water from 30 fathoms to 150-250 fathoms (depending on latitude) along the mainland coast, shoreline to 200 fathoms around most islands, except the Farallon Islands, where the fishery is closed from the shoreline to 10 fathoms) (CDF&G, 2005). Other trawl fisheries have a total trip limit of 136 kg of bycatch, which includes sea cucumbers.

There is currently no management program in Baja California. There is a fishery management proposal for Baja California, consisting of one closed season from February to May to protect the reproductive season, and another from August to October to protect the internal organs when these are absent or atrophied (Fajardo-Leon et al. 2008). There is another proposal to close fishery areas where densities are below 0.2 ind/m2 (Salgado-Rogel et al. 2009).